1. Field of the Invention
This invention relates generally to the field of packaging bulk products such as paint, bulk chemicals or bulk foodstuffs. More specifically, this invention relates to an improved stackable container assembly that is configured to ensure accurate positioning and registration between respective container assemblies when they are stacked.
2. Description of the Related Technology
In the past, bulk substances such as paint, bulk chemicals such as granular chlorine or bulk foodstuffs such as grains or sugar were typically packaged using rigid metal containers. Recently, however, plastic containers have been introduced for use in such applications.
Plastic containers tend to be less expensive than metal containers, but are not as strong and are more prone to flexure than a metal container of comparable volume. Such flexure may occur as a result of internal pressure changes relative to ambient external pressure, or as a result of physical loads that are applied to the containers. One common physical load that is applied to containers is the vertical top load that is created when like containers are stacked on top of each other. When plastic containers are stacked, it is very important that each container be accurately centered with respect to the underlying container so that forces are evenly distributed on the contact surfaces and in the sidewall portions of the respective containers. Asymmetry during stacking can contribute to container failure, particularly when exacerbated by unwanted flexure that is caused by other factors. In addition, accurate centering during stacking is important for aesthetic reasons, especially in retail settings.
A need exists for an improved plastic container assembly that is configured so as to ensure accurate registration during stacking and so as to minimize unwanted container distortion that might otherwise occur as a result of relative pressure changes between the interior of the container and ambient conditions.